Labels that we place on panels are based on the premise that the line side protective devices (the main protection) operates, however, panels lack the internal barriers and the arc flash could propagate to the line side, in which the main breaker will not operate, however there has not been any testing performed on this premise.

1. Should we at least consider the line side hazard risk category, especially when the personnel will be racking out the main?

2. How do we go with the labeling, I think it'll be confusing for the personnel to have both a load side and line side label, I say the bus side label would suffice, any thoughts?

My opinion

We have Line Side labels and Load side labels. Line side is of course the line side of the main. If doing any task involving the main the line side label is king. However when doing tasks only associated with downstream breakers from the main the Load side label is what we use. People still put lables in the wrong spot during construction so we have to be very careful to read what the label says and know very well what it applies to. I like the two labels. I do not like placing too much information on a single lable.

Unless the equipment has been built with substantial barriers (i.e. ANSI switchgear and MCCs) we always use only the LINE SIDE results on our lables.

My opinion is that, line side and load side labels are for 'barrier protected" equipment, typically switchgears only, and it is required so that electricians working on the line side need higher PPE, but if they move to the load side they won't have to suit up to make the job frustrating, having line side and load side labels for every single equipment would confuse the worker, I don't think load side label would make sense anyway since even if the worker is working on the load side, the arc flash might propagate to the line side and he'll have a false sense of protection.

I personally think line side and load side labels should be used for equipment with internal barriers if necessary, and as for the rest of the equipment, we'd use bus side, and warn the client not to use the label for line side work in the training (e.g. racking out the main). For racking the main, they could first disconnect the primary protection on the line side of the upstream feeder, IEEE1584 equations are based on the premise that upstream protection will trip and we should probably go with the standards, any thoughts?

We only use line side calculations. This provides for worst case and there is no confusion about the labels.

I dislike "Line side" since it is ambiguous. Any particular line may be going to source or a load. If a system is purely radial, suggest using "source side" and "load side."

I'm confused how "Line Side" is Ambiguous... Panels, switches, starters, etc all reference "Line" (L1, L2, L3) and "Load" (T1, T2, T3 - not in panels). If you don't know what those terms mean, call the qualified person to help you through them.

Seeing the faults

After seeing and repairing shorts between phase to phase on the line side of the main breakers, the utility fuse in both was blown.

On one location the short caused the entire industrial park to lose power as the substation tripped, and not the fuse protecting the transformer for the site that had the fault.

Another the current through the cables was 0 amps, and the fuse on the pole did it's job.. The transformer was a write off..

glen1971 -
I am confused on how your reply relates to the OP's question. Are you saying that this incident was caused by confusion between Line (Source) side and Load side?

My apologies.. Deleted the irrelevant one...

All the devices you mentioned are likely to have lines connecting them to both source and load. Some of the more relevant definitions from IEEE 100:

line (1) (electric power) A component part of a system extending
between adjacent stations or from a station to an adjacent
interconnection point. A line may consist of one or more circuits.
(5) (A) A circuit connecting two or more devices.
(C) A wire or set of wires over which a current is propagated.

None of the definitions speak of source or supply or exclude load. I maintain that "source" or "supply" side removes any ambiguity in the case of radial systems.

I agree with stevenal. I've had confusion with the line side designation where I've assumed that the "line side" of a feeder breaker was on the side away from the bus (connected to the outgoing line), but what was meant was the source side (connected to the bus).

Maybe it's because I'm used to utility substations. I think Line and Bus sides or Source and Load sides. Line and Load sides are ambiguous to me.